Reuters: Some European birds will have to fly further as global warming shifts their breeding grounds northwards in the biggest challenge to the tiny migrants since the Ice Age, scientists said on Wednesday. Some types of warbler would have to add 400 kms (250 miles) to twice-yearly trips up to 6,000 kms to and from Africa, according to the report which said it was the first to examine the potential impact of climate change on avian migration. “For some birds the extra distance might …